AbstractThe 4‐methoxybenzyl thioether protecting group is deblocked efficiently by oxidation with the homogeneous electron transfer agent tris(4‐bromophenyl)ammoniumyl (2.⊕) leading to the disulfide in high yields.S‐(4‐methoxybenzyl)cysteine derivatives like9in this way can be transformed into the corresponding cystine derivatives like10in 90% yield. Many N and carboxy protecting groups like the Boc and Z group andtert‐butyl or benzyl ester functions are stable under the cleavage conditions. On the other hand the 4‐methoxybenzyl thioether protecting group is totally unaffected by the conditions for oxidative deblocking of theS‐trityl functions by either iodine or rhodanolysis. This opens up new opportunities for the directed synthesis of cystinyl peptides with more than one intra‐ or interchain disulfide bridge. Application of the new method to the synthesis of a cystine peptide with one intrachain SS‐bridge and a double‐chain biscysti